Field of the Invention
The invention relates in general to phase difference compensation, and more particularly, to sampling phase difference compensation.
Description of the Related Art
Communication technologies (e.g., orthogonal frequency division multiplexing (OFDM)) adopting in-phase and quadrature-phase modulation methods frequently encounter IQ mismatch (or IQ imbalance), which has a particularly great effect on circuits using a zero intermediate frequency (ZIF) structure. To solve IQ mismatch, currently known technologies detect and compensate mismatch associated with frequency and mismatch unassociated with frequency. The mismatch associated with frequency is caused by a low-pass filter (LPF) in a transmission path of in-phase signals and an LPF in a transmission path of quadrature-phase signals, and the mismatch unassociated with frequency is caused by a modulator in a transmission path of in-phase signals and a modulator in a transmission path of quadrature-phase signals. For example, the compensation result is reflected by an image rejection ratio (IRR). Referring to FIG. 1 showing an IRR curve obtained by currently known technologies, the IRR curve changes with time and displays a linear relationship. The definition of the above IRR curve is generally known to one person skilled in the art. Discovered from the IRR curve in FIG. 1, currently known technologies need yet to improve.